No purple beans start out purple, turn green when cooked. I have not grown that specific variety but Johnny's description matches my past experience with other

We planted some of the Amethyst as well and they did indeed start out purple. Nope, bought the seeds at Walmart and planted them middle of May. The picture on the packet definitely shows them as being purple but they are so not purple as they're growing. Can't figure it out.

Obviously wrong seeds in the packet.